<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>科技感四角边框</title>
    <style>
        body {
            display: flex;
            justify-content: center;
            align-items: center;
            background-color: rgba(136, 146, 255, 0.303);
            width: 100%;
            height: 100vh;
            /* 隐藏页面超出部分 */
            overflow: hidden;
        }

        .box {
            width: 300px;
            height: 300px;

            /* 四角边框 */
            box-shadow: 0 0 1.5vw #1f69b9b9 inset;
            background: linear-gradient(#33cdfa, #33cdfa) left top,
                linear-gradient(#33cdfa, #33cdfa) left top,
                linear-gradient(#33cdfa, #33cdfa) right top,
                linear-gradient(#33cdfa, #33cdfa) right top,
                linear-gradient(#33cdfa, #33cdfa) left bottom,
                linear-gradient(#33cdfa, #33cdfa) left bottom,
                linear-gradient(#33cdfa, #33cdfa) right bottom,
                linear-gradient(#33cdfa, #33cdfa) right bottom;
            background-repeat: no-repeat;
            background-size: 0.1vw 1.5vw, 1.5vw 0.1vw;
        }
    </style>
</head>

<body>
    <div class="box"></div>
</body>

</html>